porting main Gaze file, #9

src/Gaze/Gaze.fs

@@ -0,0 +1,64 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+module Gaze
+
+type Gaze<'input> = {
+    content: 'input array
+    mutable offset: int
+}
+
+type Nibbler<'input, 'output> = Gaze<'input> -> 'output option
+
+let private explode (s:string) =
+        [| for c in s -> c |]
+
+/// Create an instance of Gaze that works with a String as input. 
+let fromString string = {
+    content = explode(string)
+    offset = 0
+}
+
+let fromArray array = {
+    content = array
+    offset = 0
+}
+
+let isComplete gaze = gaze.offset >= Array.length(gaze.content)
+
+let peek gaze = 
+    if isComplete gaze then
+        None
+    else
+        Some(gaze.content[gaze.offset])
+
+let next gaze = 
+    if isComplete(gaze) then
+        None
+    else
+        let result = gaze.content[gaze.offset]
+        gaze.offset <- gaze.offset + 1
+        Some(result)
+
+let check nibbler gaze =
+    let startOffset = gaze.offset
+    let res = nibbler gaze
+    gaze.offset <- startOffset
+    res
+
+let attempt nibbler gaze =
+    let startOffset = gaze.offset
+    match nibbler gaze with
+        | Some(res) -> Some(res)
+        | None ->
+            gaze.offset <- startOffset
+            None
+
+let offset gaze = gaze.offset
+
+let map nibbler mapper gaze =
+    match attempt nibbler gaze with
+        | Some(result) ->
+            Some(mapper(result))
+        | None -> None